Electrical means for detecting and announcing contact between two conducting bodies.



NO. 801,132. PATENTED OOT. 3,1905. M. BARR.

ELECTRICAL MEANS FOR DETECTING AND ANNOUNGING CONTACT BETWEEN TWOCONDUCTING BODIES.

APPLICATION FILED MAY 31, 1901.

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. UNITE STATES PATENT QFFTCE.

MARK BARR, OF KENSINGTON, ENGLAND, ASSIGNOR TO THE LINOTYPE COMPANY,LIMITED, OF LONDON, ENGLAND.

ELECTRICAL MEANS FOR DETECTING AND ANNOUNCING CONTACT BETWEEN TWOCONDUCTING BODIES.

Specification of Letters Patent.

Patented Oct. 3, 1905.

Application filed May 31, 1901. Serial No. 62,615.

To all whont it may concern:

Be it known that 1, MARK BARR, residing at No. 25 Kensington CourtGardens, Ken? sington, in the county of Middlesex, England, haveinvented a certain new and useful Improved Electrical Means forDetecting and Announcing Contact Between Two Conducting Bodies; and I dohereby declare the following to be a full, clear, and exact descriptionof the invention, such as will enable others skilled in the art to whichit appertains to make and use the same.

The present invention consists in improved electrical means fordetecting and announcing contact between two conducting bodies.

It is specially applicable to machine-tools for cutting in which boththe cutting-tool and the piece to be out are of conducting material.

In some machine-tools of this class-such, for

instance, as are used for engraving-the detection of the fact ofmechanical contact be tween the tool-point and the work is of graveimportance. An electric annunciator is the means best suited forattaining this object; but the extreme delicacy of the cutting-toolsfrequently employed in these machines prohibits the use of anyannunciator requiring for its operation a current sufficiently strong tospark across the gap between the cuttingtool and the work either justbefore contact between them is made or just after the said contact isbroken, as any such sparking would instantly fuse the point of the tool.Ordinary annunciators generally necessitate the employment of anelectric current which is capable of sparking across a gap of at least aquarter of a thousandth of an inchthat is to say, these annunciatorsoperate when the parts to be put in mechanical contact are short ofcontact by any distance not exceeding thatabove mentioned. As thepresent invention applies to machines involving an exactitude indimension up to a ten-thousandth of an inch, it cannot admit as a partof it one of the said ordinary annunciators nor,indeed,any annunciatorrequiring a current capable of giving any spark whatever, for, as abovementioned, the sparks would burn the toolpoint. It is well known thatthe type of minimum-current electrical annunciator that excites any ofthe human sensory nerves is represented by the telephone. Now the weakcurrent of a telephone will not spark, and, moreover, the graduations ofits sounds are readily audible. For instance, if foreign matter, sucheven as particles of steel, are clinging to the tool-point these,although suflicing to close the circuit, give, nevertheless, adistinctive sound as of loose moving particles, thus enabling theoperator to distinguish perfectly between a spurious and a genuinecontact. The spurious contact makes a grating sound, while the genuinecontact between the toolpoint and the face of the punch-blank is asingle sharp sound.

The accompanying diagram illustrates the invention.

1 is a part of the frame of the machine; 2, the work to be cut; '3, thecutting-tool; 4, its holder; 5, its driving-pulley, and 6 the device bywhich the tool 3 can be moved to and from the work 2 and which slides in7, an extension of the machine-frame from which it is insulated by theinsulation 8.

9 is a telephone, and 10 11 the terminals, to which its conductors 12 13are respectively connected. The terminals are mounted upon anyconvenient part of either the machineframe 1 or the extension 7, beinginsulated therefrom.

14 is the battery, and the battery-circuit is completed through theconductor 15, the work 2, the tool 3, the holder 4:, the wire 16, theterminal 11, the conductor 13, the telephone 9, the conductor 12, theterminal 10, and the conductor 17, the said current being open whenthere is no electrical contact between the tool 3 and the work 2 andclosed when there is such contact. The character of the battery and theresistance of the battery-circuit are such that only a small current canpass.

I claim 1. The combination with the cutter and the work of amachine-tool, of a battery; a telephone; a battery-circuit including thesaid cutter, work, and telephone; and a make and break consisting ofmeans by which the tool and the work can be brought into mechanicalcontact with each other or separated from each other.

2. In an engravingmachine, a contact-detector comprising an electricalcircuit including therein an annunciator, a routing-tool and an opposedcontact whereby contact of said tool with said opposed contact willactuate said annunciator.

In witness whereof I have hereunto set my hand in the presence of twowitnesses.

MARK BARR.

T/Vitnesses:

TVALTER J. SKERTEN, CHAS. S. WOODROFFE.

